Are there any difference in these two sentences when using "and" instead of comma in a list?
There is no difference in meaning. (2) is the more usual style (though whether to include a comma after "minutes" is another style choice; I would omit it). They did not add these extra hours and minutes and seconds.
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There is no difference in meaning. (2) is the more usual style (though whether to include a comma after "minutes" is another style choice; I would omit it).
Please note that this is incorrect spacing:
1.They did not add these extra hours and minutes and seconds.
This is correct spacing:
1. They did not add these extra hours and minutes and seconds.